Concept

Atheist Moral Realism Objection

Intro

The Christian moral argument runs roughly: objective moral facts exist (torturing kids for fun really is wrong, not just culturally taboo), and you need God to ground them. So if morality is real, theism is true.

This page deals with the sophisticated atheist counter-move: "Wait, I agree moral facts are real, but I don't need God to explain them. They're brute features of reality, like the laws of logic or mathematical truths. So your argument fails on me." This position is called atheist moral realism, and it is held by serious philosophers (Erik Wielenberg, Russ Shafer-Landau, David Enoch, the late Derek Parfit). It is the most sophisticated counter to the moral argument on offer.

It is also one of the most fragile positions in modern philosophy, for a few reasons. First, J.L. Mackie (an atheist) famously called moral facts "queer." On naturalism, the universe is a closed system of physical causes. Moral facts are not physical. So an atheist who accepts them is conceding the kind of non-natural reality that naturalism was supposed to rule out. He has theism's metaphysical bill without theism's explanation for it.

Second, Sharon Street (another atheist) presses what is called the evolutionary dilemma. If our moral beliefs were shaped by natural selection (which the atheist must say), they were shaped for reproductive fitness, not for tracking objective moral truth. So why think they track real moral facts? Either our moral beliefs miss the real facts (skepticism) or we have to claim an unexplained cosmic coincidence between fitness-shaped beliefs and freestanding moral reality. Neither is comfortable.

Third, on theism the so-called brute facts have an obvious home: God's character and commands. The moral order is real because the Real has a character. Atheist moral realism keeps the conclusion ("moral facts exist") while throwing away the cleanest available explanation.

Quick reply: "Granting moral realism is good. But you have just adopted Christianity's conclusion while refusing its premise. Where exactly do these brute moral facts live, and why do our minds happen to be tuned to them?"

In full

The objection that atheism is fully compatible with moral realism, that objective, mind-independent, binding moral facts can exist as brute features of reality without God as their grounding source, and therefore the Christian "moral argument" (which claims theism is required to ground objective morality) fails. Typical formulation: "I'm an atheist AND a moral realist. There ARE objective moral facts, torturing children for fun is really wrong, not just culturally relative, and I don't need God to explain them. They're brute facts, like the laws of logic. So your moral argument doesn't get traction with me."

This page treats the objection at the metaethical-philosophical level. The formal defeater syllogism in debate-prep shape lives at Atheist Moral Realism Defeater.

The position itself (steel-manned)

Atheist moral realism (also called non-theistic moral realism, secular moral realism, or Wielenberg-style robust ethics) is held by significant contemporary philosophers:

Erik Wielenberg, Robust Ethics: The Metaphysics and Epistemology of Godless Normative Realism (Oxford, 2014), the most-developed defense; coined "godless normative realism"
Russ Shafer-Landau, Moral Realism: A Defence (Oxford, 2003), major metaethical work; non-naturalist realism
David Enoch, Taking Morality Seriously: A Defense of Robust Realism (Oxford, 2011), the "robust realism" framing
Derek Parfit, On What Matters (Oxford, 3 vols, 2011-2017), sustained defense of non-naturalist normative realism; Parfit famously argued at end of life that objective moral facts exist and theism doesn't add anything to grounding them

The position holds:

Objective moral facts exist (mind-independent, not culturally-relative, not subjective)
These facts are non-natural (not reducible to physical / chemical / biological facts)
These facts are necessary (true in all possible worlds)
These facts are binding on persons
All of the above without God, the moral facts are simply brute features of reality requiring no further explanation

The position is sophisticated and held by serious philosophers. It is NOT a strawman; the Christian apologetic must engage it on its merits.

The objection's structure

The argument typically runs:

The Christian Moral Argument requires that objective morality cannot be grounded apart from God.
But objective morality CAN be grounded as brute features of reality (Wielenberg / Shafer-Landau / Enoch / Parfit).
Therefore the Christian Moral Argument fails.
Therefore atheism does not have the moral-grounding problem the Christian apologist alleges.

The deployment is typically:

Sophisticated atheist response to the Moral Argument, used by trained philosophers and informed atheists who have engaged the metaethical literature
Counter to the "atheist has no morals" charge, the atheist realist agrees morality is objective; they just deny the theistic grounding
Borrowed-capital deflection, used to argue Christians don't have a monopoly on objective morality

Important: this is NOT a logical contradiction

Strictly: the position is not logically self-contradictory. Atheist moral realism is internally consistent at the formal level, held seriously by major contemporary philosophers, defended in the technical literature.

The Christian apologetic should NOT overclaim "this is a contradiction." That move loses credibility with informed atheists. The actual apologetic frames are:

Explanatory inadequacy, the position is theoretically possible but explanatorily impoverished compared to theism
Borrowed capital, the atheist realist is using moral concepts (mind-independent normativity, binding obligations, reliable moral cognition) that have a natural home in theism and a strained one in naturalism
The Sharon Street Darwinian Dilemma, the strongest single argument, made by an atheist philosopher
Bullet-biting concessions, Wielenberg and others ADMIT they accept brute moral facts without further explanation; that admission is the apologetic point of leverage

The four load-bearing critiques

1. The grounding problem (the Mavrodes / Adams / Craig / Ritchie cluster)

Where do these moral facts come from? What grounds their existence? Wielenberg's answer: they don't come from anywhere; they're brute features of reality, like the laws of logic. The objection-to-the-objection: brute facts of this kind are explanatorily extravagant.

The atheist realist must affirm: mind-independent normative facts exist necessarily, in all possible worlds, prior to and independent of any Mind, with no further explanation. This is a substantial metaphysical commitment that:

Cannot be derived from physical / chemical / biological description (the is-ought gap, Hume's problem)
Cannot be derived from facts about human beings (or you slip into moral relativism)
Cannot be derived from evolution (which selects for survival, not truth, see Sharon Street below)
Cannot be derived from rational reflection alone (or moral disagreement would be reflective failure, which seems implausible)

Theism supplies a clean answer: moral facts are grounded in God's nature (essential moral perfection); the imago Dei anthropology explains why humans apprehend them; the divine-command tradition explains why they bind. Atheist realism leaves all three points unexplained, not contradictory, but explanatorily abandoned.

George Mavrodes ("Religion and the Queerness of Morality," 1986) and Robert Adams (Finite and Infinite Goods, 1999) developed the argument formally: a Russellian world (purely physical, no God) cannot supply the modal force that objective moral obligation requires. Wielenberg-style realism posits the modal force without explaining its source.

2. Sharon Street's Darwinian Dilemma (the killshot, atheist-internal critique)

The strongest argument against atheist moral realism comes from Sharon Street herself, an atheist philosopher (Sharon Street, "A Darwinian Dilemma for Realist Theories of Value," Philosophical Studies 127, 2006). The argument:

The atheist realist accepts evolutionary biology
Our moral beliefs were shaped by natural selection
Natural selection selects for survival (reproductive fitness), not for truth
So our moral beliefs were shaped to track survival-conducive states, NOT mind-independent moral truths
The atheist realist then faces a forced dilemma:

(a) Deny the alignment between our evolved moral beliefs and the alleged mind-independent moral truths → conclude our moral beliefs are unreliable → SKEPTICAL conclusion → realism collapses (you have no access to the moral facts even if they exist)
(b) Affirm the alignment → owe an explanation for why selection-for-survival happened to align with selection-for-moral-truth → this is a coincidence of staggering size with no naturalistic explanation

Street herself takes horn (a), she becomes a metaethical anti-realist (constructivist). Wielenberg, Enoch, Shafer-Landau try to take horn (b), they propose various explanations for the alignment (e.g., Wielenberg's "third-factor" account where moral facts and our evolved moral beliefs are both explained by some third factor). Critics, including Street, argue these explanations are ad hoc and ultimately unsuccessful.

Plantinga's variant (similar to his EAAN against naturalism + cognition generally): if our cognitive faculties were selected for survival not truth, we have a defeater for our moral beliefs that we cannot rebut from within naturalism.

The Darwinian Dilemma is the apologetically decisive argument. It comes from an atheist philosopher, it operates from premises the atheist realist accepts, and it forces a binary choice that collapses one or the other commitment (realism or naturalism).

3. Mackie's "queerness" (atheist-internal admission)

J.L. Mackie, Ethics: Inventing Right and Wrong (1977), committed atheist philosopher, argued that objective moral facts would be both metaphysically and epistemologically queer (strange) under naturalism:

Metaphysically queer: objective values would be entities of a very strange sort, irreducibly normative, mind-independent, motivationally efficacious. They don't fit anywhere in the naturalist ontology.
Epistemologically queer: how could we possibly come to know them? Some special faculty of moral intuition would be needed, and naturalism doesn't have a clean account of such a faculty.

Mackie's response was to embrace error theory, there are no objective moral facts; all positive moral judgments are false. Wielenberg-style atheist realism just bites the queerness bullet, accepts that objective moral facts are metaphysically and epistemologically queer, but insists they exist anyway as brute features of reality.

The apologetic point: even Mackie, committed atheist, no theistic axe to grind, saw the queerness as decisive enough to drive him to error theory. The Wielenberg position bites a bullet a more-rigorous atheist refused to bite. You can quote Mackie against your atheist opponent.

4. The bindingness problem

Even granting brute moral facts exist, why are they binding on persons? A fact doesn't bind; only an agent who legitimately demands binds.

"Torturing children for fun is wrong", granted as fact.
Why am I obligated to comply with this fact?

Wielenberg's answer: brute normativity. The fact just IS binding. Critics: this leaves the bindingness mysterious.

Theism supplies the binder: God as the legitimate moral authority who issues binding commands grounded in His own nature (divine-command theory) or as the ultimate good toward which we are ordered (natural-law / virtue ethics). Atheist realism leaves the bindingness floating, facts that allegedly demand compliance with no demander.

This is the gap Robert Adams (Finite and Infinite Goods, 1999) and C. Stephen Evans (God and Moral Obligation, 2013) develop formally, the move from moral value (which arguably could be brute) to moral obligation (which seems to require a relational structure with a legitimate demander).

The borrowed-capital observation

The atheist moral realist is treating four features of reality as given:

Mind-independent normativity
Binding moral obligations
Reliable moral cognition
Necessary moral truths

Each feature has:

A clean explanation under theism: God's nature grounds normativity; God's commands bind; the imago Dei explains reliable moral cognition; God's necessary existence grounds necessary moral truths
A strained explanation under naturalism: brute facts (1, 4); unexplained bindingness (2); evolved-for-survival cognition tracking truth by coincidence (3)

This is the Stealing from God Argument structural move applied to metaethics: the atheist realist is using the moral framework that has its natural home in theism while denying the theistic source. Polemical: "You've kept Christian metaethics and discarded its grounding." The atheist realist is, in Tom Holland's framing (Dominion, 2019), swimming in Christian water while denying the existence of the ocean.

Christian philosophical resources

George Mavrodes, "Religion and the Queerness of Morality" (1986), the queerness argument applied to moral obligation
Robert Adams, Finite and Infinite Goods (Oxford, 1999), the foundational modern defense of theistic metaethics
William Lane Craig (multiple essays + debates with Sam Harris, Erik Wielenberg, Shelly Kagan), the popular-level deployment of the moral argument; ground-clearing against atheist-realist responses
C. Stephen Evans, God and Moral Obligation (Oxford, 2013), the contemporary divine-command-style defense; explicitly engages Wielenberg
Mark Murphy, God and Moral Law (Oxford, 2011), natural-law theistic metaethics
Angus Ritchie, From Morality to Metaphysics: The Theistic Implications of Our Ethical Commitments (Oxford, 2012), argues only theism explains the conjunction of (a) reliable moral cognition + (b) mind-independent moral facts
Plantinga, Warrant and Proper Function + various essays, the EAAN-style argument applied to moral cognition

Apologetic deployment

Don't overclaim "contradiction", atheist moral realism is not logically self-contradictory; that move loses credibility with informed atheists. The apologetic is explanatory inadequacy, not logical incoherence.
Lead with the Sharon Street Darwinian Dilemma, strongest single argument, atheist-internal, forces a binary choice. Most informed atheists are at least aware of the dilemma; many haven't worked through it carefully.
Press the grounding problem, "What MAKES these moral facts exist? Not 'they exist', what's their truth-maker?" Force the bullet-biting; the answer "they're brute" is itself the apologetic point.
Quote Mackie, atheist-internal admission of metaphysical queerness; uses an atheist's authority against an atheist position.
Press the bindingness gap, "A fact doesn't bind; only an agent legitimately demanding binds. What's your binder?"
Close with the borrowed-capital observation, the atheist realist is using a Christian metaethical framework while denying the source.